Lithographic plate for offset and direct printing.



.l. GRASS.

LITHOGRAPHIC PLATE FOR OFFSET AND DIRECT PRINTING.

APPLlCATlON FILED JULY 24. 1914.

1,15,352. "Patented 0 t.5,1915.

' WITNESSES: v l/VI/E/VTOR JACOB GRASS, OE FULHAM, LONDON, ENGLAND.

LITHOGRAPHIC PLATE FOR OFFSET AND DIRECT PRINTTNG.

Application filed July 24; 1914. Serial No. 852,867.

. is to enable the plate to ca rry more ink than hitherto, therebyimparting a deeper color to theprint obtained from the plate, eitherdirectly or through the medium of an offset surface.

In the usual method of providing ametal lithographic plate with aprinting surface,

the greasy printing surface is applied to the surface of the plate bymeans ofa transfer, obtained in the Well-known manner, Whereafter thesurface of the plate surrounding the various portions of the printingsurface, is cleaned from scum by means of a liquid. This lattertreatment'is called etching. al-' though not etching in the literalsense. The printing surface of an ordinary metal lithographic plateconsists of a greasy substance on the surface of the plate.

Now according to the present invention, the printing surface of a metallithographic plate is etched intaglio into the plate, whereby theprinting surface, consisting of intaglio recesses, can. ta'ke up andimpart more ink, than the mere surface printing surfaces hithertoprovided on lithographic plates.

The intaglio printing surface is formed on the metal lithographic plate,by printing photographically through a positive transparency on asensitized-colloid film coating the plate, and afterward etching theplate through the exposed and treated film.

The figure of the drawings is an illustration on an enlarged scale of alithographic invention.

In said figure the numeral 1 designates a thin flat plate of metal whichforms the ordinary lithographic plate, such as zinc or aluminum, havinga groove or depression '2 therein, constituting an intaglio portion ofthe plate which is coated with varnish as j shown at 3 within saidgroove, said coating of varnish covering the bottom of the depression,while the ink designated by the nu- Specification of Letters Patent.

plate made in accordance with the Pate 1 m'eral 4. is filled into. thegroove over the.

varnish which serves as a mat to hold a maximum quantity of the ink andwhich extends to the surface of the plate.

The process is as follows:'A zinc or aluminium lithographic plate iscoated with a sensitive colloid film, such as fish glue sensitized witha bichromate. A positive transparency, rendered suitably opaque, isplaced on the sensitized film. For producing a direct printing plate thetransparency is placed face downward on the plate, for producing anofi'set printing plate, the transparency is placed face uppermostandaway from the plate, the transparency being suitably thin. Onexposure to light, the portions of the sensitized coating of the platewhich are beneath the transparent portions of the transparency harden.After removal of the transparency, the plate is washed with water whichdissolves away the unhardened portions of the coating of the plate, andthe plate is dipped in a dye bath, for instance a bath of methyl violetdye, to render the picture or the like now on the plate visible. Afterbeing dried, the plate is immersed from 2-3 minutes invan etching bath,for instance a perchlorid of iron bath. The usual etchers precautions inhaving the etching liquid of the correct consistency should be'observed.After etching, the hardened glue or the like film is softened by dilutedhydrochloric acid -or other means,

and the plate'is dried. The intaglio portions of the plate can then befilled in with lithographic ink, but to cause the ink to hold better inthe recesses, and impart a deeper color to the print obtained from theplate a varnish which is not dissolved by water or grease, such ascelluloid varnish, is first rubbed into the recesses or intaglioportions of the plate. Celluloid varnish being a mat varnish alsoprovides a holdfast for the ink block or set-up type, by type-writing orother suitable manner and rendered sufficiently opaque by dusting overwith a suitable powder. The positive transparency can for example beproduced by making an impression from a printing surface upon gelatintracing paper, or this medium has the type-written matter directly typedthereon. The transparency is then dusted over with an opaque powder,such as powdered graphite, bronze, silver or the like powder, which,owing to the powder adhering to the varnish of the impression or typedmatter, renders the same opaque.

I claim 1. A method of producing a printing surface on a metallithographic plate, consisting of coating said plate with a sensitizedfilm, exposing said film to light through a positive transparency,washing said plate after removal of said transparency, drying saidplate, etching said plate, softening said film after said etching andremoving the same, drying said plate, applying varnish insoluble inwater or grease to the etched recesses of said plate, and filling saidrecesses with lithographic ink to a plane coincident with the face ofthe plate, said varnish serving as a mat to hold a maximum quantity ofink, thereby imparting a deeper color to the print obtained fromtheplate.

2. A method of producing a printing surface on a metal lithographicplate, consisting in coating said plate with a, sensitized colloid film,exposing said film to light through a positive transparency, washingsaid plate after removal of said transparency, drying said plate,etching said plate, softening said film after said etching, drying saidplate, applying celluloid varnish to the etched recesses of said plateand filling said varnished recesses with lithographic ink and, removingthe film.

3. A method of producing a printing surface on a metal lithographicplate, consisting in coating said plate with a sensitized film, exposingsaid film to light through a transparency, washing said plate afterremoval of the transparency, drying said plate, etching said plate,softening said film after said etching, drying said plate, applyingcelluloid varnish to the etched recesses of said plate, filling saidvarnished recesses with said lithographic ink, removing said film bywashing around the recesses and gummingsaid plate to prevent oxidation.

4. The process of producing an intaglio printing surface-on a metallithographic plate, consisting in coating the same with asensitivecolloid film in the form of a glue, placing a 'positivetransparency on the sensitized film rendered suitably opaque, hardeningthe portions of the sensitized coating of the plate which are locatedbeneath the transparent portions of the transparency, dissolving awaythe unhardened portions of the coating of the plate by washing withwater, dipping the plate in a dye bath to render the picture or the likethereon visible, drying the plate, immersing the same in an etchingbath, softening the hardened glue like film and removing the same, thendrying the plate and filling the intaglio portions of the plate withlithographic ink.

5. The process of producing an intaglio printing surface on a metallithographic plate, consisting in coating the same with a sensitivecolloid film in the form of a glue, placing a positive transparency onthe sensi-' tized film rendered suitably opaque, hardening the portionsof the sensitized coating of the plate which are located beneath thetransparent portions of the transparency, dissolving away theunhardenedportions of the coating of the plate by washing with water, dipping theplate in a dye bath to render the picture or the like thereon visible,drying the plate, immersing the same in an etching bath, softening thehardened glue like film, removing said film, then drying the plate andworking celluloid varnish into the intaglio portions of the plate andthen filling said intaglio portions with lithographic ink over the saidvarnish, whereby the latter being a mat varnish, will cause the ink toenter the pores thereof to produce a deeper color than is otherwiseobtainable.

In testimony whereof I afiix my signature in presence of two witnesses.

Rom. A. BLAKE, F. W. LANE.

